The rotor system of an aircraft, such as a helicopter or tiltrotor aircraft, can act as a source of vibration during operation of the aircraft. The aircraft can include a vibration isolation or suppression system to attenuate the vibration as it is transmitted from the rotor system to the airframe. Isolating the vibration as it is transmitted to the airframe can serve to mitigate material fatigue, flight control problems, or other issues that can arise from excessive levels of vibration within the airframe. The amount of attenuation or isolation provided by a passive vibration isolation system can be reduced when acted upon by a vibration of a frequency outside of a designed or tuned frequency range of the passive isolation system.